/*
 * Copyright (C) 2013 Adrian Ulrich <adrian@blinkenlights.ch>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

package net.nullsum.audinaut.util.tags;

import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.HashMap;


class FlacFile extends Common {
    private static final int FLAC_TYPE_COMMENT = 4;   // ID of 'VorbisComment's

    public FlacFile() {
    }

    public HashMap getTags(RandomAccessFile s) throws IOException {
        int xoff = 4;  // skip file magic
        int retry = 64;
        int[] r;
        HashMap tags = new HashMap();

        for (; retry > 0; retry--) {
            r = parse_metadata_block(s, xoff);

            if (r[2] == FLAC_TYPE_COMMENT) {
                tags = parse_vorbis_comment(s, xoff + r[0], r[1]);
                break;
            }

            if (r[3] != 0)
                break; // eof reached

            // else: calculate next offset
            xoff += r[0] + r[1];
        }
        return tags;
    }

    /* Parses the metadata block at 'offset' and returns
     ** [header_size, payload_size, type, stop_after]
     */
    private int[] parse_metadata_block(RandomAccessFile s, long offset) throws IOException {
        int[] result = new int[4];
        byte[] mb_head = new byte[4];
        int stop_after;
        int block_type;
        int block_size;

        s.seek(offset);

        if (s.read(mb_head) != 4)
            xdie("failed to read metadata block header");

        block_size = b2be32(mb_head, 0);                         // read whole header as 32 big endian
        block_type = (block_size >> 24) & 127;                  // BIT 1-7 are the type
        stop_after = (((block_size >> 24) & 128) > 0 ? 1 : 0); // BIT 0 indicates the last-block flag
        block_size = (block_size & 0x00FFFFFF);                 // byte 1-7 are the size

        // debug("size="+block_size+", type="+block_type+", is_last="+stop_after);

        result[0] = 4; // hardcoded - only returned to be consistent with OGG parser
        result[1] = block_size;
        result[2] = block_type;
        result[3] = stop_after;

        return result;
    }

}
